Methods of making insulated conductors



V. S. MARTIN Filed March 24, 1955 INVENTOR. Ymm u s. MAR T//v A fro/wf yApril 21, 1959 METHODS OF MAKING INSULATED CoNDUCToRs --Unid StatesPatent O METHODS OF MAKING INSULATED CONDUCTORS Victor S. Martin,Towson, Md., assignor to Western Electric Company, Incorporated, NewYork, N.Y., a corporation of New York Application March 24, 1955, SerialNo. 496,418 7 Claims. (Cl. 154--2.24)

This invention relates to methods of making insulated conductors, andmore particularly to methods of making flexible tinsel conductors.

In the manufacture of certain types of tinsel conductors for use incommunication devices, a plurality of tinsel ribbons are wrapped invarious ways around textile strands, a cover of non-conductive materialis knitted therearound and an outer covering of plastic insulatingmaterial is formed over the conductors while the knitted covering holdsthem in place. It has been found desirable to eliminate the knitting oeration and to cover the twisted tinsel threads with longitudinallyextending strands of material, such as cotton or the like. However, itwould be diicult to maintain a plurality of longitudinal strands of thisnature positioned around the conductors uniformly during the forming ofthe outer covering.

It is, therefore, an object of this invention to provide new andimproved methods of making insulated conductors.

Another object of this invention is to provide new and improved methodsof making iexible tinsel conductors.

A method of making insulated conductors illustrating certain features ofthe invention may include positioning a plurality of conductive strandsalong an axis, positioning strands held together by a binding materiallongitudinally of the axis and around the conductive strands, forminginsulation around the material-held strands, and dissolving the bindingmaterial.

Other objects and advantages of the invention will appear from thefollowing detailed description of a method of making insulatedconductors forming a specic embodiment thereof, when read in conjunctionwith the appended drawings, in which: ,p

Fig. 1 Vis a fragmentary view of a exible conductor embodying theinvention;

Fig. 2 is a schematic diagram of an apparatus with which methodsembodying the invention may be practiced, and l vFig. 3 is an enlarged,fragmentary section taken along line 3 3 of Fig. 2. Y Y l Referring nowto the drawings, a flexible tinsel conductor consists of a plurality offlexible tinsel threads 11-11 wrapped helically around a center ycord12. Fig. l shows six of such threads 11-11, but any number could bewound around the cord 12. The individual tinsel threads 11-11 havestranded cores 15-15 composed of a multiplicity of textile strands, suchas cotton or the like. Inner layers 16-16 of tinsel ribbons, preferablyof material having high conductivity and flexibility, such as copper,bronze, or the like, are wound in a somewhat helical fashion tightlyabout the stranded cores 15-15. Outer layers 17-17 of similar tinselribbons are wound in identical fashion over the inner layers 16 16. Itwill be noted that the outer layers 17-17 are so positioned as to coverthe interstices between adjacent convolutions of the inner layers 16-16.As far as the tinsel ribbons 16--16 and 17-17 are concerned, thestranded cores 15-15 are chiefly designed to provide tensile strengthand to relieve the tinsel ribbons themselves of tensile stress, and atthe same time afford minimum resistance to ilexure.

A tape 20 is formed into a tube tinsel conductor 10. The tape 20consists of a plurality of strands 22-22 (Fig. 3), preferably of textilethread spun from cotton, or the like, placed in side-by-side positionand secured together by a binding material 23. The binding material 23may be a heat-dissolving adhesive, such as glue, a thermoplasticmaterial, or the like. The material 23 forms the body of the tape 20with the strands 22-22 spaced uniformly across the tape and embeddedtherein. The tape 20 is formed into a longitudinally extending tube 21,whereby the strands 22-22 are positioned uniformly around the ilexibletinsel conductor 10 so that the axes of the strands are parallel to theaxis of the center cord 12, and the strands are so held initially by thebinding material 23. A covering 25 of insulating material is formed by asuitable process, such as extrusion, around the tube 21. The insulatingmaterial 25 may be a vulcanizable material, such as a compound ofrubber, neoprene or the like, or it may be a thermoplastic material,such as polyvinyl chloride, polyethylene, or the like.

ln Fig. 2, apparatus is disclosed which may be utilized in performingthe objects of the invention. A supply 'reel is shown at 26 to provide asupply of the conductor 10 consisting of the twisted tinsel threads11-11 wound helically around the center cord 12, as described above. Asupply pad 27 of the tape 20 is provided, and the tape is passedtherefrom over a guide roller 30 and through a suitable tube formingdevice 31, which forms the tape into the tube 21 around the flexibletinsel conductor 10. The flexible tinsel conductor 10 and the tube 21formed therearound are then passed as a unit through an extrudingmachine 32, and the covering 25 is extruded around the tube 21. Thecompleted conductor is wrapped around a capstan 35 which draws theconductor through the extruding machine 32, and iinally is Wound on atakeup reel 36.

The tape 20, which consists of the longitudinal threads 22-22 heldtogether initially by the binding material 23, is relatively stiff atroom temperature and may be formed 21 around the flexible at will.ductor.

As hereinbefore stated, the binding material 23 of the tape 20 may be anadhesive, such as glue, a suitable thermoplastic material, or othermaterial capable of bindingtthe strands together, but which decomposes,disintegrates or melts at a temperature no higher than that reached inthe extruder. If the material is made of glue, the glue Willdisintegrate in the extruder 32 when the covering 25 is formedtherearound, be reduced to small particles of powder-like form, and bedispersed within the covering. If the binding material is made of athermoplastic material, the material will melt during the extrudingoperation and may become integral with the covering 25. When apolymerized thermoplastic material is utilized to form the covering 25,it may be desirable to use the same material of lower polymerization, oranother low melting point plastic, for the binding material 23, so thatthe binding material will melt at a temperature lower than that to whichthe covering material will be heated during the extrusion operation. Byso doing, the material 23 will be assured of melting within the covering25. When the term dissolving is used herein and in the annexed claims,it is intended to mean a decomposition, disentegration or melting of thebinding material, as distinguished from the dissolving of a material ina solvent.

If the covering 25 is a vulcanizable material, such as rubber, neoprene,or the like, a vulcanizing chamber of conventional design wouldbe placedbetween the extruder 32 and the capstan 35 to cure the material. 1f thecovering 25 is a thermoplastic material, a Water trough may be placedtherebetween to cool the material.

'Ihe spacing between the strands 22-22 is greatly exaggerated inthedrawings, and in fact is quite small. These strands, while lendingflexibility to the nished tinsel conductor 1), also contribute greattensile strength thereto, They act further as a` barrier between themetallic tinsel ribbons 16-16, 17-17 and the extruded covering 25. Thisbarrier is necessary if, for example, the tinsel ribbons are made ofcopper or bronze and the covering of rubber has some sulfur therein. Thesulfur would have a corrosive effect on the copper or bronze and thiseffect is prevented by interposing the strands 22-22 between the two.The strands also act as a mechanical barrier to protect the tinselribbons 16--16 and 17--17 against damage by crushing or othercompressive forces to which the conductor may be subjected in use.

It is manifest that the invention is not limited to the preferredembodiments hertofore described and various modications may be madewithin the spirit and scope of the invention. Thus, the covering 25 maybe applied in any manner as long as the requirement is satisfied thatsuicient heat be generated during such application to dissolve thebinding material 23.

Also, it is evident that the tinsel conductor may comprise a singletextile core around which a plurality of tinsel ribbons are helicallyYwound. For example, four tinsel ribbons may be wound around a textilecore and the tape 20 and outer covering 25 applied therearound, ashereinbefore described.

What is claimed is:

1. The method of making insulated conductors, which comprisespositioning a along an axis, positioning strands held together by abinding material disintegrable at a predetermined temperature parallelto said axis and around said conductive strands, and forming insulationaround said material-held strands at a temperature at least as high assaid predetermined temperature so that said binding material isdisintegrated. f

2. The method of making insulated conductors, which comprisespositioning a plurality of conductors along an axis, forming a tube `oftogether by a heat-disintegrable binding material disintegrable at apredetermined temperature around said conductors and parallel to saidaxis, and forming a plastic covering around said non-conductors at atemperature at least as high as said predetermined temperature such thatthe said material is disintegrated.

i 3. The method of making insulated conductors, which comprisespositioning a plurality of conductors together, forming a tube ofnon-conductive strands secured together by a thermoplastic materialdisintegrable at a predetermined temperature around said conductors andlongitudinally with respect thereto, forming a covering of inpluralityof conductive strands sulating material around said tubeat at least saidpredetermined temperature, and disintegrating said thermo plasticmaterial during the formation of said covering.

4l The method of making insulated conductors, which comprisespositioning a plurality of conductive strands along an axis, positioningstrands held together by glue disintegrable at a predeterminedtemperature longitudinally of said axis and around said conductivestrands, form ing a covering of insulation around said glue-held strandsat at least said predetermined temperature, and disintegrating said glueduring the formation of said covering.

5. The method of making flexible conductors, which comprises winding aplurality of conductors helically around a center core, forming a tubeof textile strands secured together by an adhesive disintegrable at apredetermined temperature around said conductors so that the axes ofsaid strands are parallel to the axis of said center core, forming acovering of plastic material around said tube at at least saidpredetermined temperature, and causing said adhesive to disintegrateduring the formation of said covering.

6. The method of making tinsel conductors, which cornprises winding aplurality of tinsel ribbons helically around textile strands to formtinsel strands, winding a plurality of said tinsel strands helicallyabout a center textile'core, forming around said wound tinsel strands atube made of a tape comprising thermoplastic material disintegrable at apredetermined temperature in which is embedded a plurality of textilestrands having axes parallel to the axis of the core, and extruding anouter covering around said tube at a temperature at least as high assaid predetermined temperature such that said thermoplastic materialdisintegrates.

7. The method of making flexible tinsel conductors, which compriseswinding la plurality of ilat tinsel ribbons helically around a cottonthread to form a tinsel strand, winding a plurality of said tinselstrands helically around a center textile core, forming a tape made ofilexible, parallel cotton strands held together by glue disintegrable ata predetermined temperature longitudinally into a tube around saidhelically wound tinsel strands, passing said tube-covered tinsel strandsthrough an extruding device to extrude a covering of insulation'materialtherearound at at least said predetermined temperature, anddisintegratnon-conductive strands secured ing said glue during theextruding of said covering so that said glue is dispersed and saidcotton strands are relatively free.

References Cited in the tile of this patent UNITED STATES PATENTS

1. THE MEHTOD OF MAKING INSULATED CONDUCTORS, WHICH COMPRISESPOSITIONING A PLURALITY OF CONDUCTIVE STRANDS ALONG AN AXIS POSITIONINGSTRANDS HELD TOGETHER BY A BINDING MATERIAL DISINTEGRABLE AT APREDETERMINED TEMPERATURE PARRALLEL TO SAID AXIS AND AROUND SAIDCONDUCTIVE